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Rare childhood cancers may be linked to heavy smog exposure

Smog may cause kids to develop cancer.

A new study presented April 9 at the American Association for Cancer Research annual meeting in Washington, D.C. revealed that traffic pollution and three rare childhood cancers may be linked.

"Much less is known about exposure to pollution and childhood cancer than adult cancers," Julia Heck, an assistant researcher in the school's epidemiology department and a member of UCLA's Jonsson Comprehensive Cancer Center, said in a press release. "Our innovation in this study was looking at other, more rare types of childhood cancer, such as retinoblastoma, and their possible connection to traffic-related air pollution."

UCLA researchers looked at data on 3,950 children born between 1998 and 2007 and who were part of the California Cancer Registry. The children were all diagnosed with cancer before they were 6 years old.

Using a state modeling program called CALINE4, they were able to estimate how much traffic pollution the children were exposed to. CALINE4 uses data from gasoline and diesel vehicles within a 1,500-meter radius buffer, traffic volumes, roadway geometry, vehicle emission rates and weather to come up with pollution models. The researchers were then able to determine how much pollution a child was exposed to during each trimester of their mom's pregnancy and throughout the first year of life.

The study revealed that higher exposure to traffic-related air pollution increased the chance the child had acute lymphoblastic leukemia (white blood cell cancer) by 4 percent. There was also a 17 percent increased risk in germ-cell tumors (cancers of the testicles, ovaries and other organs), and a 14 percent higher risk of retinoblastoma (eye cancer). Children with retinoblastoma had a 19 percent increased incidence of bilateral retinoblastoma -- where both eyes are affected -- if they were exposed to high levels of pollution.

Rates of the blood-related cancer non-Hodgkin's lymphoma and tissue-related cancer ependymoma (which affects the brain and spinal chord) were also higher, but the numbers were not statistically significant.

No specific period looked at was linked to higher incidences of these cancers, so scientists were unable to determine if a certain time during development was more dangerous to be exposed to pollution than others.

The study is considered preliminary because it was presented at a medical conference, and hasn't been published yet in a peer-reviewed journal.

Some doctors pointed out that mothers shouldn't be too worried about their child's cancer risk because the study only found a link and did not show direct cause and effect. They may want to be more worried about other health risks like asthma. A recent study showed that up to 14 percent of chronic childhood asthma may be due to being in environments with high traffic pollution.

"There has been an association between air pollution and other diseases," Dr. Rubin Cohen, director of the Adult Cystic Fibrosis and Bronchiectasis Center at the Long Island Jewish Medical Center in New Hyde Park, N.Y., told HealthDay. "We know that pollution causes asthma, and that is probably more real than the cancer issue."

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